In the United States, it is estimated that 2.2 million people age 40 and older have glaucoma, with 120,000 suffering blindness [1] (see List of Cited References, below). Most glaucoma patients are associated with abnormally high intraocular pressure (IOP) due to the patient's inability to drain excessive aqueous humor from the anterior chamber of the eye through the trabecular meshwork. If not reduced with adequate treatment, the high IOP would continuously suppress and damage the optic nerve as the disease progresses, leading to loss of vision or even total blindness. Current clinical treatment involves medication typically in the form of eye drops with dosages depending on the severeness of the disease. However, this treatment is accompanied by certain concerns such as difficulty of continuous treatment, inefficient dosage style, and potential side effects or patient refractoriness to the drug composition. Glaucoma drainage devices (GDD) present a potentially desirable alternative to continuous treatment with eye drops. GDD's function by providing an artificial drainage path so as to reduce the IOP. GDD's usually comprise a plurality of valves to regulate IOP within a prescribed range. Different kinds of on-chip surface-micromachined parylene-based check valves have been investigated with the potential application of using them as IOP regulators. The aforementioned technology, however, does not exist as a stand-alone device which can be implanted in a patient's eye in a minimally-evasive manner.
Thus, a continuing need exists for an implantable glaucoma drainage device which can regulate intraocular pressure.
List of Cited References:
[1] Glaucoma Research Foundation, www.glaucoma.org
[2] P. J. Chen, D. C. Rodger, E. M. Meng, M. S. Humayun, and Y. C. Tai, “Surface Micromachined Parylene Dual Valves for On-Chip Unpowered Microflow Regulation,” J. Microelectromech. Syst., vol. 16, pp. 223-231, 2007.
[3] P. J. Chen, and Y. C. Tai, “Floating-Disk Parylene Micro Check Valve,” Proc. MEMS 2007 Conference, Kobe, Japan, Jan. 21-55, 2007, pp. 453-456.
[4] P. J. Chen, D. C. Rodger, M. S. Humayun, Y. C. Tai, “Floating-Disk Parylene Microvalve for Self-Regulating Biomedical Flow Controls,” Proc. MEMS 2008 Conference,Tucson, Ariz., USA, Jan. 13-17, 2008, pp. 575-578.
[5] P. J. Chen, D. C. Rodger, S. Saati, J. C. Altamirano, C. H. Lin, R. Agrawal, R. Varma, M. S. Humayun, and Y. C. Tai, “Implementation of microfabricated sutureless flexible parylene tissue anchors on minimally invasive biomedical implants,” Proc. MicroTAS 2007 Conference, Paris, France, Oct. 7-11, 2007, pp. 518-520.